Not at all harder, actually. Almost irrelevant. They look at your academic record, and your GMAT score, plus any work experience (which is highly recommended. The best MBA programs generally prefer at least 5 years of experience after college)
Take a look at this profile of the Harvard MBA class of 2016:
http://www.hbs.edu/mba/admissions/class-profile/Pages/default.aspx
Notice average age of 27 (about 5 years out of college)
Notice GMAT scores and GPA.
Notice all the state schools… nope, they don’t mention that because it doesn’t matter.
Also, I see that you have been accepted to both Georgia Tech and Johns Hopkins. No need to stress, those two schools are extremely highly respected. You can accomplish anything with a degree from either one. At Johns Hopkins you will probably work harder than at Northwestern (or Harvard). JHU is very proud of its demanding curriculum.